Ferrule coupling for joining ducts together

ABSTRACT

An apparatus comprising an inner ferrule and an outer ferrule. The inner ferrule comprises a plurality of engagement sections that define a plurality of gaps between the plurality of engagement sections. The outer ferrule is disposed around at least a portion of the inner ferrule. The outer ferrule comprises an engagement area mechanically joined to the plurality of engagement sections to join the inner ferrule to the outer ferrule.

FIELD

The present disclosure relates generally to a ferrule coupling forjoining together lines, such as ducts, and, more particularly, to anapparatus and method for joining an outer duct and an inner duct using aferrule coupling assembled using two ferrules or three ferrules.

BACKGROUND

Certain applications may require the use of lines, pipes, or ducts withmultiple walls. As one example, an aircraft may have fuel lines formedby dual wall duct systems. For example, a fuel line may include an innerduct and an outer duct that are joined to each other with the outer ductspaced apart from the inner duct. In some cases, the inner duct may beused for a fluid of a first type, while the outer duct may be used for afluid of a second type. In other cases, the inner duct may be used for amain flow of fluid, while the outer duct may be used to contain leakageor vapors released from the inner duct. A coupling may be used to bothjoin the inner duct and the outer duct and control a distance betweenthe inner duct and the outer duct. For example, a coupling may be usedto ensure that the outer duct is spaced apart from the inner duct toallow a flow of fluid or provide a containment volume between the innerduct and the outer duct.

Some currently available couplings for joining an inner duct and anouter duct use two ferrules that are welded together at one or more weldlocations. Over time, the performance of the coupling at these one ormore weld locations may decline due to temperature changes, stress, orother factors. For example, the coupling may become susceptible tocracking or separation at the one or more weld locations. Further,welding the two ferrules together makes welding or other permanentmethods of joining the ferrules to prevent for disassembly of thecomponents once joined. Thus, one or more apparatuses and methods forferrule couplings unaffected by heat-based stresses may be desired.

SUMMARY

In one example embodiment, an apparatus comprises an inner ferrule andan outer ferrule. The inner ferrule has a plurality of engagementsections that define a plurality of gaps between the plurality ofengagement sections. The outer ferrule has an engagement area disposedaround at least a portion of the inner ferrule and mechanically joinedto the plurality of engagement sections to join the inner ferrule to theouter ferrule.

In another example embodiment, another apparatus is provided. Theapparatus comprises an inner ferrule, an intermediate ferrule, and anouter ferrule. The intermediate ferrule includes a plurality ofengagement sections. The intermediate ferrule is disposed around atleast a portion of the inner ferrule and is mechanically joined to theinner ferrule. The outer ferrule includes an engagement area disposedaround at least a portion of the intermediate ferrule. The engagementarea is mechanically joined to the plurality of engagement sections.

In yet another example embodiment, a method is provided. The method mayinclude coupling an outer duct to an outer ferrule. A plurality ofengagement sections of an inner ferrule is joined to an engagement areaof the outer ferrule. Further, an inner duct is joined to the innerferrule. The outer ferrule may be disposed around the inner ferrule.

In still yet another example embodiment, a method is provided for movingfuel through a duct system in an aircraft. The fuel is moved through aninner duct that is joined with an outer duct through a joining of aninner ferrule attached to the inner duct and an outer ferrule attachedto the outer duct. A leakage from the fuel flowing through the innerduct is captured within a region that is formed between the inner ductand the outer duct by a plurality of engagement sections of the innerferrule that protrude radially outward from the inner ferrule and thatdefine a plurality of gaps between the plurality of engagement sections.

The features and functions may be achieved independently in variousembodiments of the present disclosure or may be combined in yet otherembodiments in which further details may be seen with reference to thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, and furtherobjectives and features thereof, will best be understood by reference tothe following detailed description of an illustrative embodiment of thepresent disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of a perspective view of an aircraft inaccordance with an example embodiment.

FIG. 2 is an illustration of an isometric view of a duct system formedusing a ferrule coupling in accordance with an example embodiment.

FIG. 3 is an illustration of an isometric exploded view of the ductsystem from FIG. 2 in accordance with an example embodiment.

FIG. 4 is an illustration of a cross-sectional view of the duct systemfrom FIG. 2 in accordance with an example embodiment.

FIG. 5 is an illustration of a side exploded view of the duct systemfrom FIG. 4 in accordance with an example embodiment.

FIG. 6 is an illustration of a front view of the duct system from FIG. 2in accordance with an example embodiment.

FIG. 7 is an illustration of a rear view of the duct system from FIG. 2in accordance with an example embodiment.

FIG. 8 is an illustration of a cross-sectional view of an inner ferrulein accordance with an example embodiment.

FIG. 9 is an illustration of a cross-sectional view of an outer ferrulein accordance with an example embodiment.

FIG. 10 is an illustration of an isometric view of a duct system formedusing a ferrule coupling having a different configuration in accordancewith an example embodiment.

FIG. 11 is an illustration of an isometric exploded view of the ductsystem from FIG. 10 in accordance with an example embodiment.

FIG. 12 is an illustration of a cross-sectional view of the duct systemfrom FIG. 10 in accordance with an example embodiment.

FIG. 13 is an illustration of a side exploded view of the duct systemfrom FIG. 12 in accordance with an example embodiment.

FIG. 14 is an illustration of a front view of the duct system from FIG.10 in accordance with an illustrative embodiment.

FIG. 15 is an illustration of a cross-sectional view of an inner ferrulein accordance with an example embodiment.

FIG. 16 is an illustration of a cross-sectional view of an intermediateferrule in accordance with an example embodiment.

FIG. 17 is an illustration of a cross-sectional view of an outer ferrulein accordance with an example embodiment.

FIG. 18 is a flowchart illustration of a process for assembling a ductsystem in accordance with an example embodiment.

FIG. 19 is a flowchart illustration of a process for assembling a ductsystem in accordance with an example embodiment.

FIG. 20 is a flowchart illustration of a process for moving fuel througha duct system in an aircraft in accordance with an example embodiment.

DETAILED DESCRIPTION

The illustrative examples provide a duct system that uses a ferrulecoupling formed using multiple ferrules. This multi-piece ferrulecoupling may be used to connect an inner duct and an outer duct to forma duct system in which the outer duct is spaced apart from the innerduct. The outer duct may form an encapsulated shroud around the innerduct. The ferrule coupling described in the illustrative examples may beformed using at least two ferrule components that are assembled to formthe ferrule coupling without welding. The ferrule coupling forms anelectrostatic bond path between the inner duct and the outer duct. Thistype of ferrule coupling may be robust and may reduce or eliminate theneed for rework of each ferrule component, thereby allowing theelectrostatic bond path to be maintained. Further, this multi-pieceferrule coupling may have a longer service life than a ferrule couplingformed by welding two ferrules together.

With reference now to the figures, FIG. 1 is an illustration of anaircraft, depicted in accordance with an illustrative embodiment.Aircraft 100 includes wing 102 and wing 104 attached to fuselage 106.Aircraft 100 includes engine 108 attached to wing 102 and engine 110attached to wing 104. Aircraft 100 also includes tail section 112.Horizontal stabilizer 114, horizontal stabilizer 116, and verticalstabilizer 118 are attached to tail section 112.

Aircraft 100 is an example of one type of platform that includes ductsystems that include multi-piece ferrule couplings in accordance withthe illustrative embodiments described below. For example, withoutlimitation, aircraft 100 may include a fuel system that includes fuellines that at least partially include duct systems joined together withmulti-piece ferrule couplings in a manner similar to duct system 200 ofFIG. 2 below or duct system 1000 of FIG. 10 below.

In these illustrative examples, aircraft 100 takes the form of arefueling aircraft, such as a tanker, having refueling boom 120. Fuelmay be transferred from aircraft 100 to another aircraft or other typeof vehicle or platform through refueling boom 120. A duct system, suchas duct system 200 in FIG. 2 or duct system 1000 in FIG. 10 below, maybe used with fuel lines that are located within the refueling aircraftor outside the refueling aircraft. For example, these types of ductsystems may be used with fuel lines that are connected to or locatedwithin refueling boom 120.

In other illustrative examples, aircraft 100 may be some other type ofaircraft and one or more duct systems implemented similar to duct system200 of FIG. 2 may be used to transport fuel or other fluids or gaseswithin an inner duct. The outer duct may then serve to lock in anyfluids or gases that leak from the inner duct. As such, an inner ductmay be disposed within an outer duct, ferrules may be used to jointogether the inner duct and the outer duct and dispose the outer duct ina fixed spatial relationship to the outer duct.

Such ferrules may include a multi-piece ferrule coupling with two,three, or four or more ferrule components. As the components of such amulti-piece ferrule coupling may be mechanically joined together,electrostatic bonding is not needed to join together the components. Inthis way, areas of the ferrules weakened from heat-based stresses ofelectrostatic bonding may be prevented. For the purposes of thisdisclosure, “joining” may refer to one or both of direct coupling (e.g.,two components that are directly connected and, thus, contacting oneanother) or indirect coupling (e.g., two components that are held in oneor more fixed spatial relations to each other through one or more othercomponents). Thus, “join” or “joining” may also be referred to as“couple” or “coupling,” herein.

A technical effect of the illustrative embodiments described hereinincludes reduced maintenance of fuel lines. For example, the multi-pieceferrule couplings may reduce or eliminate the need for rework of eachferrule component. Further, the duct systems using these types offerrule couplings may be stronger and more reliable over time becausethe ferrule couplings include at least one interface between themultiple ferrules of the multi-piece ferrule coupling that is strongerand more resistant to temperature-based stresses, cracking, and/or otherinconsistencies as compared to ferrule couplings in which all ferruleinterfaces are formed by welding.

Thus, a technical effect of the illustrative embodiments describedherein includes duct systems that are more reliable compared totraditionally manufactured ducts, such as ducts with welded ferrules.Further, even after rework, the ferrule couplings described by theillustrative embodiments herein do not weaken or eliminate anelectrostatic bond path between the inner and outer ducts of the ductsystem. Accordingly, these ferrule couplings, and thereby the ductsystems using these types of ferrule couplings, may have longer servicelives.

FIGS. 2-9 are illustrations of different views of duct system 200 andcomponents of duct system 200. Duct system 200 is a multi-walled ductsystem that uses a dual ferrule coupling.

With reference now to FIG. 2 is an illustration of an isometric view ofa duct system formed using a ferrule coupling in accordance with anexample embodiment. Duct system 200 may include at least two ducts andmay include any number of ferrules, ferrule couplings, or combinationthereof. In one illustrative embodiment, duct system 200 includes innerduct 202, outer duct 204, and ferrule coupling 206. Ferrule coupling 206is used to mechanically join inner duct 202 and outer duct 204.

Ferrule coupling 206 includes inner ferrule 208 and outer ferrule 210.Inner ferrule 208 is joined to inner duct 202. When inner ferrule 208 isjoined to inner duct 202, inner ferrule 208 may be disposed around, oroverlap, at least a portion of an exterior (not shown) of inner duct202. Outer ferrule 210 is joined to outer duct 204. When outer ferrule210 is joined to outer duct 204, outer ferrule 210 may be adjacent to,surround, or overlap at least a portion of exterior 212 of outer duct204.

The joining of inner ferrule 208 to inner duct 202 and outer ferrule 210to outer duct 204 may be performed using any number of techniquesincluding, but not limited to, at least one of welding, electrostaticbonding, adhesive bonding, swaging, or some other type of process. Forexample, inner duct 202 may be swaged within inner ferrule 208. In someillustrative examples, outer ferrule 210 is welded to outer duct 204 atweld interface 214. Weld interface 214 may be formed using, for example,a butt welding technique. For example, weld interface 214 may be formedwhere an edge of outer ferrule 210 abuts an edge of outer duct 204.

Inner ferrule 208 may be joined with outer ferrule 210 to thereby joininner duct 202 with outer duct 204. As depicted, when inner ferrule 208and outer ferrule 210 are joined, outer ferrule 210 may at leastpartially overlap inner ferrule 208.

In these illustrative examples, inner ferrule 208 may be mechanicallyjoined with outer ferrule 210. A first component, such as inner ferrule208, may be “mechanically joined” to a second component, such as outerferrule 210, either directly or indirectly. Further, mechanicallycoupling two components may mean coupling the two components, withoutwelding. In some cases, mechanically joining two components creates anelectrostatic bond between the two components. Inner ferrule 208 may bemechanically joined to outer ferrule 210 via threading, friction fit,swaging, bolting, insertion of at least one dowel in a correspondingopening, adhesive, some other mechanical coupling technique, or acombination thereof.

FIG. 3 is an illustration of an isometric exploded view of duct system200 from FIG. 2 in accordance with an example embodiment. As depicted,inner duct 202, outer duct 204, inner ferrule 208, and outer ferrule 210may be substantially cylindrical. Further, when assembled to form ductsystem 200, inner duct 202, outer duct 204, inner ferrule 208, and outerferrule 210 may be substantially coaxial with respect to axis 300.

Inner ferrule 208 extends between end 301 and end 302. As depicted,inner ferrule 208 has inner surface 303 and outer surface 304. Innerferrule 208 includes body 305 and plurality of engagement sections 306disposed along outer surface 304. In these illustrative examples,plurality of engagement sections 306 may be a plurality of discrete,discontinuous engagement sections disposed substantiallycircumferentially around body 305 of inner ferrule 208 at or near end302 of inner ferrule 208. In particular, each of plurality of engagementsections 306 may be located at a different position along outer surface304 of body 305 of inner ferrule 208.

In these illustrative examples, plurality of engagement sections 306 mayprotrude or extend radially outwards from body 305 relative to axis 300.Engagement section 307 is an example of one of plurality of engagementsections 306. Engagement section 307 has a selected height such thatengagement section 307 protrudes outward.

Plurality of engagement sections 306 defines plurality of gaps 308between plurality of engagement sections 306. When inner ferrule 208 isjoined to outer ferrule 210, plurality of gaps 308 helps define openingsthrough which fluid may flow. Further, each of plurality of engagementsections 306 has threads. For example, engagement section 307 hasthreads 309.

In one illustrative example, inner ferrule 208 includes grooves 310disposed on inner surface 303 of body 305 of inner ferrule 208. Grooves310 are disposed along inner surface 303 between end 301 and end 302. Inthis illustrative example, grooves 310 are disposed along a middleportion of inner surface 303 located between end 301 and end 302 ofinner ferrule 208. As depicted, grooves 310 may extend fully aroundinner surface 303 of body 305 of inner ferrule 208. In some illustrativeexamples, grooves 310 may extend only partially around inner surface303. In other illustrative examples, without limitation, grooves 310 mayextend in a discontinuous manner around inner surface 303 to formmultiple grooved areas along inner surface 303.

Inner duct 202 may be fit at least partially within inner ferrule 208using grooves 310. For example, without limitation, grooves 310 may takethe form of swage grooves. Inner duct 202 may be swaged (e.g., rollerswaged) within inner ferrule 208 using grooves 310 (e.g., swage grooves)to form a swaged joint between inner ferrule 208 and inner duct 202.

Outer ferrule 210 extends between end 312 and end 314. As depicted,outer ferrule 210 has inner surface 316 and outer surface 318. Outerferrule 210 includes body 320 and engagement area 322. Engagement area322 of outer ferrule 210 may be a substantially continuous area, orfeature, disposed along inner surface 316 of body 320 of outer ferrule210. In this illustrative example, engagement area 322 is located alonga middle portion of inner surface 316 between end 312 and end 314. Inthese illustrative examples, engagement area 322 may extend fully aroundinner surface 316 of body 320 in an annular manner. In otherillustrative examples, engagement area 322 may be disposed onlypartially around inner surface 316 or may be formed in a discontinuousmanner around inner surface 316.

Plurality of engagement sections 306 of inner ferrule 208 may be engagedwith engagement area 322 to join inner ferrule 208 to outer ferrule 210.In other words, engagement area 322 may be mechanically joined toplurality of engagement sections 306 to join inner ferrule 208 to outerferrule 210.

Engagement area 322 may include threads 324 disposed along inner surface316 of outer ferrule 210. In these illustrative examples, the threads oneach of plurality of engagement sections 306 may be sized and shaped forengagement with threads 324 of engagement area 322 of outer ferrule 210.In other words, threads 324 may correspond with the threads of pluralityof engagement sections 306. For example, threads 309 of engagementsection 307 may be sized and shaped for engagement with threads 324. Inother words, threads 309 may correspond to threads 324.

In these illustrative examples, inner duct 202, outer duct 204, innerferrule 208, and outer ferrule 210 may each be comprised of one or morematerials including, but not limited to, metal and metal alloys. Body305 of inner ferrule 208 may be comprised of a material that is harderthan the material forming inner duct 202 to allow for swaging. In somecases, body 305 of inner ferrule 208 may also be comprised of a materialthat is harder than the material forming body 320 of outer ferrule 210.For example, without limitation, body 305 of inner ferrule 208 may becomprised of a first aluminum alloy, such as 2024-T851 aluminum, whilebody 320 of outer ferrule 210 may be comprised of a second aluminumalloy, such as 6061-T6 aluminum.

FIG. 4 is an illustration of a cross-sectional view of duct system 200taken with respect to lines 4-4 in FIG. 2 in accordance with an exampleembodiment. As depicted, inner ferrule 208 engages outer ferrule 210 tothereby join inner duct 202 with outer duct 204. A fluid (e.g., aliquid(s), a gas(es), or combination thereof) may flow through channel400 through inner duct 202. In these illustrative examples, at least oneof inner ferrule 208 or inner duct 202 defines an outer circumference ofchannel 400, which may be a first fluid volume.

In this illustrative example, inner duct 202 has been swaged withininner ferrule 208. Further, threads 309 of engagement section 307 ofinner ferrule 208 are engaged with threads 324 of engagement area 322 ofouter ferrule 210. Further, weld interface 214 between outer ferrule 210and outer duct 204 may be more clearly seen.

Ferrule coupling 206 formed by inner ferrule 208 and outer ferrule 210provides separation between inner duct 202 and outer duct 204. Inparticular, ferrule coupling 206 spaces apart outer duct 204 from innerduct 202 to define region 402 between inner duct 202 and outer duct 204.Specifically, at least one of outer ferrule 210 or outer duct 204defines an outer circumference of region 402, which may be a secondfluid volume.

Outer duct 204 may be separated from inner duct 202 in a radialdirection relative to axis 300. Region 402 may be used to collect anyleakage of fluid flowing through channel 400 within inner duct 202. Whenthe fluid flowing through inner duct 202 is fuel, region 402 may be usedto capture a leakage of the fuel or a leakage of fuel vapors. Forexample, outer duct 204 may function as a “shroud” that prevents anyleakage of fluid out of inner duct 202 from escaping duct system 200. Inother illustrative examples, region 402 may provide for the flow of afluid different from the fluid flowing through channel 400 in a same ordifferent direction.

In still other illustrative examples, channel 400 may be used fortransferring fluid and filling, while region 402 may be used forventing. As one illustrative example, when duct system 200 is usedwithin, for example, refueling boom 120 of FIG. 1, region 402 may beused to provide venting. When fuel is transferred through refueling boom120 into, for example, a fuel tank of another aircraft, vapors in thefuel tank may be pushed out as fuel fills the fuel tank. These vaporsmay be vented out of the fuel tank through region 402 between inner duct202 and outer duct 204.

The engagement of threads on plurality of engagement sections 306 fromFIG. 3 with threads 324 of engagement area 322 establishes ferruleinterface 404 between inner ferrule 208 and outer ferrule 210. Ferruleinterface 404 establishes an electrostatic bond between inner ferrule208 and outer ferrule 210, and thereby, between inner duct 202 and outerduct 204. Ferrule interface 404 may be stronger and more resistant totemperature-based stresses, cracking, and/or other inconsistencies ascompared to an interface formed by welding. Further, ferrule interface404, even if reworked later in the life of duct system 200, may becapable of maintaining the electrostatic bond between inner ferrule 208and outer ferrule 210 and thereby, between inner duct 202 and outer duct204.

FIG. 5 is an illustration of a side exploded view of duct system 200from FIG. 4 in accordance with an example embodiment. As depicted, eachengagement section of plurality of engagement sections 306 isindividually threaded. Thus, coupling inner ferrule 208 to outer ferrule210 may include threading together inner ferrule 208 and outer ferrule210 such that the threads on each of plurality of engagement sections306 engage the corresponding threads 324 of engagement area 322 of outerferrule 210.

FIG. 6 is an illustration of a front view of duct system 200 taken withrespect to lines 6-6 in FIG. 2 in accordance with an example embodiment.As depicted, plurality of gaps 308 between plurality of engagementsections 306 help define plurality of openings 600 through which fluidmay flow. Plurality of openings 600 allow fluid to flow into or out ofregion 402. For example, plurality of openings 600 may allow fluid toflow in a substantially axial direction relative to axis 300.

FIG. 7 is an illustration of a rear view of duct system 200 from FIGS.2-6 taken with respect to lines 7-7 in FIG. 2 in accordance with anexample embodiment. Plurality of openings 600 may also be visible inthis view.

FIG. 8 is an illustration of a cross-sectional view, similar to that ofFIG. 4, of only inner ferrule 208 in accordance with an exampleembodiment. Threads 309 of engagement section 307 may be more clearlydepicted in this view. Further, grooves 310 may be more clearlydepicted. Inner ferrule 208 has stop feature 800 located adjacent togrooves 310. Stop feature 800 helps provide a guide for the positioningof inner duct 202 of FIGS. 2-3 within inner ferrule 208. When inner duct202 is swaged within inner ferrule 208 in the direction of arrow 801,stop feature 800 provides a stop for this swaging action to help preventfurther swaging in the direction of arrow 801.

Inner ferrule 208 also includes outer groove 802. Outer groove 802 maybe used during the manufacturing of inner ferrule 208 (e.g., as a datapoint reference), may receive a sealing component, such as an O-ring,may be interfaced with one or more other components (e.g., may be usedto join inner ferrule 208 to a different ferrule), or a combinationthereof.

FIG. 9 is an illustration of a cross-sectional view, similar to that ofFIG. 4, of only outer ferrule 210 in accordance with an exampleembodiment. Threads 324 of engagement area 322 may be more clearlydepicted in this view. As depicted, outer ferrule 210 may includeportion 900 having a smaller diameter than the rest of outer ferrule210. Portion 900 defines stop feature 902. Stop feature 902 helpsprovide a guide for the positioning of inner ferrule 208 of FIGS. 2-3within outer ferrule 210. When inner ferrule 208 is threaded into outerferrule 210 in the direction of arrow 904, stop feature 902 provides astop for this threading action to prevent further threading in thedirection of arrow 904.

Further, outer ferrule 210 includes outer groove 906. Outer groove 906may be used during the manufacturing of outer ferrule 210 (e.g., as adata point reference), may receive a sealing component, such as anO-ring, may be interfaced with one or more other components (e.g., maybe used to join outer ferrule 210 to a different ferrule), or acombination thereof.

FIG. 10 is an illustration of an isometric view of a duct system formedusing a ferrule coupling having a different configuration in accordancewith an example embodiment. Duct system 1000 may include at least twoducts and may include any number of ferrules, ferrule couplings, orcombination thereof. In one illustrative embodiment, duct system 1000includes inner duct 1002, outer duct 1004, and ferrule coupling 1006.Ferrule coupling 1006 is used to mechanically join inner duct 1002 andouter duct 1004. In these illustrative examples, ferrule coupling 1006includes inner ferrule 1008, outer ferrule 1010, and intermediateferrule 1012.

In some cases, the intermediate ferrule 1012 may also be referred to asan inner ferrule. For example, intermediate ferrule 1012 may be a firstinner ferrule and inner ferrule 1008 may be a second inner ferrule. Thefirst and second inner ferrules may be joined together to form asub-coupling that is joined to outer ferrule 1010.

Inner ferrule 1008 is joined to inner duct 1002. Outer ferrule 1010 isjoined to outer duct 1004. Inner ferrule 1008 and outer ferrule 1010 arejoined through intermediate ferrule 1012. Accordingly, joining innerferrule 1008 with outer ferrule 1010 through intermediate ferrule 1012thereby joins inner duct 1002 with outer duct 1004. As depicted, whenduct system 1000 is assembled, outer ferrule 1010 may at least partiallyoverlap inner ferrule 1008. The joining of inner ferrule 1008 to innerduct 1002 and outer ferrule 1010 to outer duct 1004 may be performedusing a mechanical technique, electrostatic bonding, adhesive bonding,some other technique, or a combination thereof.

In some illustrative examples, outer ferrule 1010 may be positionedadjacent to and in contact with an edge of outer duct 1004. In otherillustrative examples, outer ferrule 1010 may be positioned around atleast a portion of exterior 1013 of outer duct 1004. In one illustrativeexample, outer ferrule 1010 is welded to outer duct 1004 at weldinterface 1014. Weld interface 1014 may be formed using, for example, abutt welding technique. In other illustrative examples, outer ferrule1010 may be joined to outer duct 1004 in some other manner. In somecases, inner ferrule 1008 may be welded to inner duct 1002 in a similarmanner.

In other illustrative examples, inner ferrule 1008 and outer ferrule1010 may be joined to inner duct 1002 and outer duct 1004, respectively,through swaging (e.g., roller swaging, rotary swaging, axial swaging, orsome other type of swaging) or some other joining technique. In somecases, adhesive may be used in joining inner ferrule 1008 and outerferrule 1010 to inner duct 1002 and outer duct 1004, respectively.

FIG. 11 is an illustration of an isometric exploded view of duct system1000 from FIG. 10 in accordance with an example embodiment. As depicted,inner duct 1002, outer duct 1004, inner ferrule 1008, outer ferrule1010, and intermediate ferrule 1012 may be substantially cylindrical.Further, when duct system 1000 is assembled, inner duct 1002, outer duct1004, inner ferrule 1008, outer ferrule 1010, and intermediate ferrule1012 may be substantially coaxial with respect to axis 1100.

Outer ferrule 1010 extends between end 1101 and end 1102. As depicted,outer ferrule 1010 has inner surface 1103 and outer surface 1104. Outerferrule 1010 includes body 1105 having engagement area 1106. Engagementarea 1106 is formed along inner surface 1103 of body 1105 of outerferrule 1010. Engagement area 1106 may be referred to as, in some cases,a retaining feature. In one illustrative example, engagement area 1106may be shaped and sized to form a pocket or notch for positioning andretaining at least a portion of intermediate ferrule 1012. In oneillustrative example, the engagement area 1106 includes a groove.

In this illustrative example, inner ferrule 1008 has end 1107 and end1108. Further, inner ferrule 1008 has inner surface 1109 and outersurface 1110. Inner ferule 1008 includes body 1112 having engagementarea 1114. Depending on the implementation, engagement area 1114 may bea single continuous engagement area or may be comprised of multipleengagement areas.

Inner ferrule 1008 also includes stop feature 1116 and stop feature1117. Stop feature 1116 may be located at or near end 1108. Stop feature1117 may be located at or near end 1107. In one illustrative example,stop feature 1117 is located near but spaced away from end 1107. Stopfeature 1116 may be, for example, a lip or other type of protrusion atthe edge of inner ferrule 1008 at end 1108.

In this illustrative example, engagement area 1114 is located betweenstop feature 1116 and stop feature 1117. Engagement area 1114 may bereferred to, in some cases, as a retaining feature. Engagement area 1114may be shaped and sized for receiving, positioning, and retaining atleast a portion of intermediate ferrule 1012.

As depicted, inner ferrule 1008 may include plurality of protrusions1118 that protrude outwards from body 1112 of inner ferrule 1008.Plurality of protrusions 1118 may be discrete, discontinuous protrusionsdisposed substantially circumferentially around inner ferrule 1008. Inthis illustrative example, plurality of protrusions 1118 is locatedadjacent to and extends axially away from stop feature 1117. Pluralityof protrusions 1118 does not extend all the way to stop feature 1116.

Engagement area 1114 includes plurality of retaining areas 1122 (e.g.,gaps) defined between plurality of protrusions 1118. In otherillustrative examples, plurality of retaining areas 1122 may beconsidered separate from engagement area 1114.

When duct system 1000 is assembled, intermediate ferrule 1012 ispositioned between inner ferrule 1008 and outer ferrule 1010.Intermediate ferrule 1012 helps join inner ferrule 1008 with outerferrule 1010, while also providing a spacing or separation, in a radialdirection relative to axis 1100, between inner ferrule 1008 and outerferrule 1010.

Intermediate ferrule 1012 includes body 1123, plurality of engagementsections 1124, and plurality of tab elements 1126. In one illustrativeexample, body 1123 takes the form of a band or nearly annular band. Forexample, body 1123 includes gap 1125. Plurality of engagement sections1124 are disposed along and protrude outwards from body 1123. Pluralityof engagement sections 1124 may include discontinuous engagementsections that are separated by plurality of gaps 1127. Plurality ofengagement sections 1124 may engage engagement area 1106 of outerferrule 1010. For example, when engagement area 1106 includes a groove,plurality of engagement sections 1124 may be disposed within the groovewhen duct system 1000 is fully assembled. Further, when duct system 1000is fully assembled, plurality of gaps 1127 between plurality ofengagement sections 1124 form openings (or channels) through which fluidmay flow.

Plurality of tab elements 1126 are positioned adjacent to plurality ofengagement sections 1124 and extend axially relative to axis 1100 in onedirection away from body 1123. In this illustrative example, pluralityof tab elements 1126 includes a corresponding tab element for each ofplurality of engagement sections 1124. In other illustrative examples, atab element in plurality of tab elements 1126 may be sized such that thetab element is positioned adjacent to multiple engagement sections ofplurality of engagement sections 1124.

When intermediate ferrule 1012 is joined to inner ferrule 1008,plurality of engagement sections 1124 and plurality of tab elements 1126are positioned and retained within engagement area 1114. Specifically,plurality of tab elements 1126 are positioned and retained withinplurality of retaining areas 1122. Accordingly, plurality of protrusions1118 on inner ferrule 1008 may be shaped and sized to define pluralityof retaining areas 1122 for receiving plurality of tab elements 1126. Inother words, plurality of retaining areas 1122 may be complementary toplurality of tab elements 1126.

Once intermediate ferrule 1012 is joined with inner ferrule 1008, stopfeature 1116 and stop feature 1117 may help prevent axial movement ofintermediate ferrule 1012 relative to inner ferrule 1008 relative toaxis 1100. Plurality of protrusions 1118 may help prevent rotation ofintermediate ferrule 1012 relative to inner ferrule 1008 about axis1100.

In these illustrative examples, inner ferrule 1008 and intermediateferrule 1012 may be mechanically joined via, for example, aninterference fit (or friction fit). Gap 1125 in body 1123 ofintermediate ferrule 1012 provides a degree of flexibility to body 1123that allows intermediate ferrule 1012 to be wrapped around and fit overinner ferrule 1008 with an interference fit. Gap 1125, which may also bereferred to as a discontinuity, may allow intermediate ferrule 1012 tobe deformed in a manner that allows intermediate ferrule 1012 to befitted around inner ferrule 1008. Thus, gap 1125 allows intermediateferrule 1012 to be more easily joined to inner ferrule 1008.

In one illustrative example, intermediate ferrule 1012, when no forcesare exerted on or applied to intermediate ferrule 1012, may have aninner diameter that is smaller than the outer diameter of inner ferrule1008. This difference in diameters may allow intermediate ferrule 1012to be fitted around inner ferrule 1008 with an interference fit.

In these illustrative examples, each of plurality of tab elements 1126may have a height selected such that plurality of tab elements 1126 aresubstantially flush with plurality of protrusions 1118 of inner ferrule1008 when intermediate ferrule 1012 is joined to inner ferrule 1008. Inother illustrative examples, one or more of plurality of tab elements1126 may have a height greater than or lower than plurality ofprotrusions 1118.

When inner ferrule 1008 is joined with intermediate ferrule 1012, thetwo ferrules form a sub-coupling that may then be joined to outerferrule 1010. In particular, when inner ferrule 1008 and intermediateferrule 1012 are joined to form the sub-coupling, plurality ofengagement sections 1124 may fit within and be retained withinengagement area 1106 of outer ferrule 1010.

In these illustrative examples, inner duct 1002, outer duct 1004, innerferrule 1008, intermediate ferrule 1012, and outer ferrule 1010 may eachbe comprised of one or more materials including, but not limited to,metal and metal alloys. As one illustrative example, each of inner duct1002, outer duct 1004, inner ferrule 1008, intermediate ferrule 1012,and outer ferrule 1010 may be comprised of a same or different aluminumalloy.

In these illustrative examples, plurality of engagement sections 1124 ofintermediate ferrule 1012 may be comprised of a material that providesboth sufficient compliancy and strength. In particular, plurality ofengagement sections 1124 may need to be sufficiently compliant such thatthe sub-coupling of inner ferrule 1008 and intermediate ferrule 1012 maybe inserted through outer ferrule 1010 and plurality of engagementsections 1124 may be slid into and fit within engagement area 1106 ofouter ferrule 1010. Plurality of engagement sections 1124, however, mayalso need to be sufficiently strong and hard to allow each of pluralityof engagement sections 1124 to retain its shape to maintain adequateseparation between inner ferrule 1008 and outer ferrule 1010 over time.

Intermediate ferrule 1012 is used as a structural and mechanicalseparator between inner ferrule 1008 and outer ferrule 1010.Intermediate ferrule 1012 may be joined to inner ferrule 1008 after thewelding operation has been performed to weld inner ferrule 1008 withinner duct 1002. Further, the sub-coupling formed by intermediateferrule 1012 and inner ferrule 1008 may be joined with outer ferrule1010 after the welding operation has been performed to weld outerferrule 1010 to outer duct 1004. In this manner, intermediate ferrule1012 may be used after a buildup of heat from the welding operations hasdissipated and the weld interfaces between inner ferrule 1008 with innerduct 1002 and outer ferrule 1010 to outer duct 1004 has cooled.Engagement area 1114 of inner ferrule 1008 and engagement area 1106 ofouter ferrule 1010 work together to retain intermediate ferrule 1012 aspart of ferrule coupling 1006 and within duct system 1000.

FIG. 12 is an illustration of a cross-sectional view of duct system 1000taken with respect to lines 12-12 in FIG. 10 in accordance with anexample embodiment. As depicted, inner ferrule 1008 is joined withintermediate ferrule 1012 and outer ferrule 1010. A fluid (e.g., aliquid(s), a gas(es), or combination thereof) may flow through channel1200 through inner duct 1002.

In this illustrative example, inner duct 1002 has been joined withininner ferrule 1008 through an interference fit. Intermediate ferrule1012 has been joined with inner ferrule 1008 through an interferencefit. As depicted, each of plurality of engagement sections 1124 fitswithin and is retained within engagement area 1106 of outer ferrule1010.

Ferrule coupling 1006 formed by inner ferrule 1008, outer ferrule 1010,and intermediate ferrule 1012 provides separation between inner duct1002 and outer duct 1004. In particular, ferrule coupling 1006 spacesapart outer duct 1004 from inner duct 1002 to define region 1202 betweeninner duct 1002 and outer duct 1004. Outer duct 1004 may be separatedfrom inner duct 1002 in a radial direction relative to axis 300. Region1202 may be used to collect any leakage of fluid flowing through channel1200 within inner duct 1002. For example, outer duct 1004 may functionas a “shroud” that prevents any leakage of fluid out of inner duct 1002from escaping duct system 1000. In other illustrative examples, region1202 may provide for the flow of a fluid different from the fluidflowing through channel 1200 in a same or different direction.

In still other illustrative examples, channel 1200 may be used fortransferring fluid and filling, while region 1202 may be used forventing. As one illustrative example, when duct system 1000 is usedwithin, for example, refueling boom 120 of FIG. 1, region 1202 may beused to provide venting. When fuel is transferred through refueling boom120 into, for example, a fuel tank of another aircraft, vapors in thefuel tank may be pushed out as fuel fills the fuel tank. These vaporsmay be vented out of the fuel tank through region 1202 between innerduct 1002 and outer duct 1004.

The engagement of threads on plurality of engagement sections 1124 withengagement area 1106 establishes ferrule interface 1204 between innerferrule 1008, intermediate ferrule 1012, and outer ferrule 1010. Ferruleinterface 1204 establishes an electrostatic bond between the threeferrules and thereby, between inner duct 1002 and outer duct 1004.Ferrule interface 1204 may be stronger and more resistant totemperature-based stresses, cracking, and/or other inconsistencies ascompared to an interface formed by welding. Further, ferrule interface1204, even if reworked later in the life of duct system 1000, may becapable of maintaining the electrostatic bond between inner ferrule1008, intermediate ferrule 1012, and outer ferrule 1010 and thereby,between inner duct 1002 and outer duct 1004.

FIG. 13 is an illustration of a side exploded view of duct system 1000from FIG. 12 in accordance with an example embodiment. As depicted,outer ferrule 1010 includes stop feature 1300 that helps defineengagement area 1106. Stop feature 1300 also helps provide a guide forthe positioning of the sub-coupling formed by inner ferrule 1008 andintermediate ferrule 1012 of FIGS. 10-12 within outer ferrule 1010. Whenthis sub-coupling is fit within outer ferrule 1010, stop feature 1300prevents the sub-coupling from moving further in the direction of arrow1302.

FIG. 14 is an illustration of a front view of duct system 1000 takenwith respect to lines 14-14 in FIG. 10 in accordance with anillustrative embodiment. As depicted, plurality of gaps 1127 betweenplurality of engagement sections 1124 of intermediate ferrule 1012 helpdefine plurality of openings 1400 through which fluid may flow.Plurality of openings 1400 allow fluid to flow into or out of region1202. For example, plurality of openings 1400 may allow fluid to flow ina substantially axial direction relative to axis 1100.

FIG. 15 is an illustration of a cross-sectional view, similar to that ofFIG. 13, of only inner ferrule 1008 in accordance with an exampleembodiment. As depicted, inner ferrule 1008 also includes outer groove1500. Outer groove 1500 may be used during the manufacturing of innerferrule 1008 (e.g., as a data point reference), may receive a sealingcomponent, such as an O-ring, may be interfaced with one or more othercomponents (e.g., may be used to join inner ferrule 1008 to a differentferrule), or a combination thereof.

FIG. 16 is an illustration of a cross-sectional view, similar to that ofFIG. 13, of only intermediate ferrule 1012 in accordance with an exampleembodiment.

FIG. 17 is an illustration of a cross-sectional view, similar to that ofFIG. 13, of only outer ferrule 1010 in accordance with an exampleembodiment. As depicted, outer ferrule 1010 includes outer groove 1700.Outer groove 1700 may be used during the manufacturing of outer ferrule1010 (e.g., as a data point reference), may receive a sealing component,such as an O-ring, may be interfaced with one or more other components(e.g., may be used to join outer ferrule 1010 to a different ferrule),or a combination thereof.

While the illustrative examples described herein include continuousengagement areas and discontinuous engagement sections disposed oncertain portions of the ferrules, other example embodiments includeengagement areas or engagement sections disposed on other portions ofthe ferrules. In other illustrative examples, an engagement areadescribed herein may be substituted with engagement sections, andengagement sections may be substituted with an engagement area.Corresponding engagement areas and engagement sections may bemechanically joined to each other. For example, corresponding engagementareas and engagement sections may be mechanically joined throughinterference fit, swaging, bolting, adhesive bonding, some othertechnique, or a combination thereof.

FIG. 18 is a flowchart illustration of a process for assembling a ductsystem in accordance with an example embodiment. Process 1800illustrated in FIG. 18 may be implemented using duct system 200 fromFIGS. 2-9.

Process 1800 begins by joining outer duct 204 to outer ferrule 210 (step1802). In one illustrative example, outer duct 204 may be welded toouter ferrule 210. Next, plurality of engagement sections 306 of innerferrule 208 may be mechanically joined to engagement area 322 of outerferrule 210 (step 1804).

At step 1804, mechanically joining plurality of engagement sections 306with engagement area 322 joins inner ferrule 208 to outer ferrule 210,such that outer ferrule 210 is at least partially disposed around innerferrule 208. In some illustrative examples, thread locker or some typeof sealant or adhesive may be applied to one or more of plurality ofengagement sections 306 or engagement area 322 to aid in securing innerferrule 208 and outer ferrule 210 together. In these illustrativeexamples, each of plurality of engagement sections 306 may then bethreaded together with engagement area 322. The threads on plurality ofengagement sections 306 may be torqued to a predetermined torque valueto provide adequate electrostatic bonding contact between inner ferrule208 and outer ferrule 210, and thereby inner duct 202 and outer duct204.

Inner duct 202 is joined to inner ferrule 208 (step 1806), with theprocess terminating thereafter. In one illustrative example, inner duct202 may be swaged (e.g., roller swaged) to grooves 310 disposed on innersurface 303 of inner ferrule 208. In one or more examples, this swagingmay be performed according to the Aerospace Standard set by the Societyof Automotive Engineers (SAE) (e.g., SAE AS4060).

FIG. 19 is a flowchart illustration of a process for assembling a ductsystem in accordance with an example embodiment. Process 1900illustrated in FIG. 19 may be implemented using duct system 1000 fromFIGS. 10-17.

Process 1900 may begin by joining outer duct 1004 to outer ferrule 1010and inner duct 1002 to inner ferrule 1008 (step 1902). In oneillustrative example, outer duct 1004 may be welded to outer ferrule1010 and inner duct 1002 may be welded to inner ferrule 1008. In otherillustrative examples, some other type of process may be used to performthe joining of these components. For example, in some cases, inner duct1002 may be swaged within inner ferrule 1008.

Thereafter, intermediate ferrule 1012 is joined to inner ferrule 1008 toform a sub-coupling (step 1904). This sub-coupling may also be referredto as a ferrule sub-coupling. The sub-coupling is then joined to outerferrule 1010 (step 1906), with the process terminating thereafter. Thejoining of the sub-coupling to outer ferrule 1010 joins inner ferrule1008 to outer ferrule 1010, and thereby, inner duct 1002 to outer duct1004. In some illustrative examples, the joining performed at step 1604and 1606 may be performed through interference fits. During thesejoining processes, the various stop features of inner ferrule 1008 andouter ferrule 1010 may be used to help guide and align the differentferrules relative to each other. In some illustrative examples, sealantor adhesive may be used to provide additional support and restraint.

FIG. 20 is a flowchart illustration of a process for moving fuel througha duct system in an aircraft in accordance with an example embodiment.Process 2000 illustrated in FIG. 20 may be implemented using, forexample, duct system 200 from FIGS. 2-9.

Process 2000 may begin by moving the fuel through inner duct 202 that isjoined with outer duct 204 through a joining of inner ferrule 208attached to inner duct 202 and outer ferrule 210 attached to outer duct204 (step 2002). At step 2002, inner duct 202 and outer duct 204 may atleast partially form a fuel line or portion of a fuel line system for anaircraft, such as aircraft 100 in FIG. 1. In some embodiments, theaircraft may be a refueling aircraft, such as a tanker aircraft.

A leakage from the fuel flowing through inner duct 202 is capturedwithin region 402 that is formed between inner duct 202 and outer duct204 by plurality of engagement sections 306 of inner ferrule 208 thatprotrude radially outward from inner ferrule 208 and that define aplurality of gaps 308 between plurality of engagement sections 306 (step2004), with the process terminating thereafter. At step 2004, theleakage may be a leakage of the fuel itself or a leakage of vapors. Theleakage of fuel or vapors that is captured, or collected, within region402 may be allowed to flow through plurality of gaps 308 betweenplurality of engagement sections 306.

Thus, the different example embodiments provide two differentconfigurations of ferrule couplings that may be used to join two lines,such as ducts, together. In one example embodiment, a ferrule couplingcomprises an inner ferrule and an outer ferrule. The inner ferrule has aplurality of engagement sections. The outer ferrule has an engagementarea that allows for the outer ferrule to be disposed around at least aportion of the inner ferrule and mechanically join the engagement areato the plurality of engagement sections to join the inner ferrule to theouter ferrule.

In another example, another apparatus is provided. The apparatuscomprises an inner ferrule, an intermediate ferrule, and an outerferrule. The intermediate ferrule includes a plurality of engagementsections and is disposed around at least a portion of the inner ferruleand mechanically joined to the inner ferrule. The outer ferrule includesan engagement area and is disposed around at least a portion of theintermediate ferrule. The engagement area and the plurality ofengagement sections are mechanically joined to the plurality ofengagement sections.

The flowcharts and block diagrams in the different depicted embodimentsillustrate the architecture, functionality, and operation of somepossible implementations of apparatuses and methods in an illustrativeembodiment. In this regard, each block in the flowcharts or blockdiagrams may represent a module, a segment, a function, and/or a portionof an operation or step. In some alternative implementations of anillustrative embodiment, the function or functions noted in the blocksmay occur out of the order noted in the figures. For example, in somecases, two blocks shown in succession may be executed substantiallyconcurrently, or the blocks may sometimes be performed in the reverseorder, depending upon the functionality involved. Also, other blocks maybe added in addition to the illustrated blocks in a flowchart or blockdiagram. For example, while the processes described herein detail amanufacturing process with a certain sequence of assembly, otherprocesses may include different sequences for the steps of the process,as needed.

As used herein, the phrase “at least one of,” when used with a list ofitems, means different combinations of one or more of the listed itemsmay be used and only one of the items in the list may be needed. Theitem may be a particular object, thing, step, operation, process, orcategory. In other words, “at least one of” means any combination ofitems or number of items may be used from the list, but not all of theitems in the list may be required. For example, without limitation, “atleast one of item A, item B, or item C” or “at least one of item A, itemB, and item C” may mean item A; item A and item B; item B; item A, itemB, and item C; item B and item C; or item A and C. In some cases, “atleast one of item A, item B, or item C” or “at least one of item A, itemB, and item C” may mean, but is not limited to, two of item A, one ofitem B, and five of item C; three of item B and six of item C; or someother suitable combination.

The description of the different illustrative examples has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different illustrative examplesmay provide different features as compared to other desirableembodiments. The embodiment or embodiments selected are chosen anddescribed in order to best explain the principles of the embodiments,the practical application, and to enable others of ordinary skill in theart to understand the disclosure for various embodiments with variousmodifications as are suited to the particular use contemplated.

What is claimed is:
 1. An apparatus comprising: an inner ferrulecomprising a plurality of engagement sections that define a plurality ofgaps between the plurality of engagement sections; and an outer ferruledisposed around at least a portion of the inner ferrule and comprisingan engagement area mechanically joined to the plurality of engagementsections to join the inner ferrule to the outer ferrule.
 2. Theapparatus of claim 1, wherein each of the plurality of engagementsections has threads, the engagement area comprises correspondingthreads, and the plurality of engagement sections and the engagementarea are threaded together.
 3. The apparatus of claim 2, wherein theplurality of engagement sections comprises first threads and theengagement area comprises second threads corresponding to the firstthreads.
 4. The apparatus of claim 1, further comprising: an inner ductjoined to the inner ferrule; and an outer duct disposed around at leasta portion of the inner duct and joined to the outer ferrule.
 5. Theapparatus of claim 4, wherein at least one of the inner ferrule or theinner duct define an outer circumference of a first fluid volume.
 6. Theapparatus of claim 4, wherein at least one of the outer ferrule or theouter duct define an outer circumference of a second fluid volume. 7.The apparatus of claim 4, wherein the inner ferrule comprises: a swagegroove, wherein the inner duct is joined to the inner ferrule by swaginga portion of the inner duct into the swage groove.
 8. The apparatus ofclaim 4, wherein the outer duct is joined to the outer ferrule bywelding.
 9. The apparatus of claim 4, wherein the inner ferrule, theouter ferrule, the inner duct, and the outer duct are substantiallycylindrical, the outer ferrule is disposed circumferentially around theinner ferrule, and the outer duct is disposed circumferentially aroundthe inner duct.
 10. The apparatus of claim 1, wherein the inner ferruleis a first inner ferrule and further comprising: a second inner ferrulejoined to the first inner ferrule, wherein the first inner ferrule isdisposed around at least a portion of the second inner ferrule.
 11. Theapparatus of claim 1, further comprising: an inner duct joined to theinner ferrule; and an outer duct disposed around at least a portion ofthe inner duct and joined to the outer ferrule, wherein the plurality ofengagement sections protrude from the inner ferrule such that a regionis formed between the inner duct and the outer duct.
 12. The apparatusof claim 11, wherein a leakage of vapors is collected within the regionbetween the inner duct and the outer duct when fuel is transferredthrough the inner duct.
 13. The apparatus of claim 12, wherein thevapors move through the plurality of gaps between the plurality ofengagement sections.
 14. An apparatus comprising: an inner ferrule; anintermediate ferrule mechanically joined to the inner ferrule such thatthe intermediate ferrule is disposed around at least a portion of theinner ferrule, the intermediate ferrule comprising a plurality ofengagement sections; and an outer ferrule comprising an engagement areamechanically joined to the plurality of engagement sections such thatthe outer ferrule is disposed around at least a portion of theintermediate ferrule.
 15. The apparatus of claim 14, wherein theengagement area comprises a groove and the plurality of engagementsections and the engagement area are joined via an interference fit withthe plurality of engagement sections disposed within the groove.
 16. Theapparatus of claim 14, wherein the inner ferrule comprises a pluralityof protrusions and a plurality of retaining areas between the pluralityof protrusions, wherein the intermediate ferrule comprises a pluralityof tab elements, and wherein the inner ferrule is mechanically joined tothe intermediate ferrule via an interference fit with the plurality oftab elements disposed within the plurality of retaining areas.
 17. Theapparatus of claim 14, further comprising: an inner duct joined to theinner ferrule; and an outer duct joined to the outer ferrule.
 18. Amethod comprising: joining an outer duct to an outer ferrule; andjoining, mechanically, a plurality of engagement sections of an innerferrule to an engagement area of the outer ferrule such that the outerferrule is disposed around at least a portion of the inner ferrule. 19.The method of claim 18, wherein joining, mechanically, the plurality ofengagement sections of the inner ferrule to the engagement area of theouter ferrule comprises: joining, mechanically, a first inner ferrulecomprising the plurality of engagement sections with a second innerferrule; and joining the first inner ferrule to an engagement area ofthe outer ferrule such that the outer ferrule is disposed around atleast a portion of the first inner ferrule.
 20. The method of claim 19,further comprising: joining the second inner ferrule to an inner duct.21. The method of claim 19, wherein joining, mechanically, the firstinner ferrule comprising the plurality of engagement sections with thesecond inner ferrule comprises: joining the first inner ferrule with thesecond inner ferrule via an interference fit such that the plurality ofengagement sections is disposed around at least a portion of the secondinner ferrule and such that a plurality of tab elements of the firstinner ferrule is disposed within a plurality of retaining areas of thesecond inner ferrule.
 22. The method of claim 18, further comprising:joining the inner ferrule to an inner duct.
 23. The method of claim 22,wherein joining the inner ferrule to the inner duct comprises: swagingthe inner duct into grooves of the inner ferrule.
 24. A method formoving fuel through a duct system in an aircraft, the method comprising:moving the fuel through an inner duct that is joined with an outer ductthrough a joining of an inner ferrule attached to the inner duct and anouter ferrule attached to the outer duct; and capturing a leakage fromthe fuel flowing through the inner duct within a region that is formedbetween the inner duct and the outer duct by a plurality of engagementsections of the inner ferrule that protrude radially outward from theinner ferrule and that define a plurality of gaps between the pluralityof engagement sections.
 25. The method of claim 24, wherein capturingthe leakage comprises: capturing vapors within the region formed betweenthe inner duct and the outer duct; and allowing the vapors to flowthrough the plurality of gaps between the plurality of engagementsections.